Militants fighting for the ISIS in Syria are making millions of pounds selling ancient statues and mosaics to wealthy Westerners using a complex system of smugglers and middle men.

Looted from ancient buildings in ISIS strongholds, such as the group's de facto capital city Raqqa, the antiquities are up to 10,000-years-old and can exchange hands for more than $1 million each.

The most expensive items are covertly smuggled overseas - usually on the orders of wealthy Europeans - but there is also a lucrative trade in less historically important objects, which often find their way into tourist shops and markets in neighbouring Lebanon and Turkey.

The trade in antiquities is one of ISIS' primary sources of funding, along with oil and ransom payments, and is estimated to fills the terrorists coffers with tens of millions of pounds every year.